January 17, 2013 16 Comments
In the insect world, hyperdiversity is the norm. More than a million species are known, and perhaps several million more await discovery. Beetles alone represent nearly a quarter of the earth’s described biota, with one genus (Agrilus in the family Buprestidae) bursting at the seams with more than 3,000 described species (Bellamy 2008). Biodiversity gone wild! While birders routinely field identify (and list) a majority of the birds they see to species, most insect enthusiasts are happy if they can simply identify their subjects to family—in most cases still leaving several hundred to several thousand possibilities for species identification. Even trained entomologists usually can identify only a tiny fraction of the insects they see and remain just as clueless about the vast majority of insects they encounter that don’t represent one of their limited number of study groups.
Of course, that doesn’t mean field identification is impossible for all insects—certain groups such as butterflies, dragonflies, and tiger beetles lend themselves to field identification due to their relatively large size, bright colors, and distinctive markings. Many would also include the aculeate hymenopterans (i.e., “stinging” wasps and bees) among those groups for these same reasons. However, the vast majority of hymenopterans belong to a multitude of families characterized by tiny, parasitic species that seem (to this coleopterist’s eyes) to differ only in bafflingly minute details of wing venation and tibial spurs. (Honestly, I couldn’t tell you the difference between Tanaostigmatidae and Tetracampidae if my life depended on it!) Nevertheless, there are a small handful of parasitic hymenopterans in North America that are instantly recognizable due to their giant size (2 or more inches in length)—namely, Megarhyssa spp. (giant ichneumons) and the species shown in this post, Pelecinus polyturator (American pelecinid). Pelecinus polyturator is the only North American member of the family Pelecinidae, which itself contains only two additional species that are restricted to Mexico and Central/South America. It wasn’t always this way—fossils assignable to the family and representing 43 species in a dozen genera have been found as far back as the early Cretaceous (121–124 mya) across North America, Europe, and Asia (Grimaldi & Engel 2005). Surely this represents just the tip of the iceberg of Mesozoic and early Cenozoic pelecinid diversity, making today’s three species the last representatives of a once great lineage—”living fossils”¹ some might say.
¹ To ward off any scolding I might get from evolutionary purists, I get it; there is no such thing as a living fossil (except the T. rex skeleton in the movie “Night at the Museum”). I know that all species alive today have the same amount of evolutionary history behind them and are, if not from more immediate ancestors, highly derived compared to earlier life forms. I will admit that the term has become a bit overused as pseudoscientific shorthand for branding an organism as ‘primitive’ (another term which tends to raise hackles); however, I don’t see the problem with its use as informal reference to relatively ancient groups, usually more diverse in the past and now represented by only a few species. Innocuous shorthand is all it is.
This elegant female, recognizable by her extraordinarily narrowly elongate abdomen (males have a somewhat shorter abdomen that is widened at the end), was seen back in July 2011 as she flew to a blacklight and landed on nearby foliage in a mesic bottomland forest in southeastern Missouri’s Ozark Highlands. I have seen females on occasion over the years but have not yet seen a male, which are increasingly rare in more northern latitudes of the species distribution. I missed the focus a bit on this photo (and also the other half-dozen or so shots that I took)—photographing an active subject at night on elevated foliage without a tripod is difficult to say the least! Nevertheless, after post-processing it’s a decent photograph. If you are wondering why it took me so long to post it, that’s because only recently have I gained the confidence to “clean up” poorly exposed photos where the subject and/or substrate on which they are resting is so distractingly littered with debris as this:
Compare the original photo here to the final photo above it—how many post-processing tools can you detect the use of?
Bellamy, C. L. 2008. World catalogue and bibliography of the jewel beetles (Coleoptera: Buprestoidea), Volume 4: Agrilinae: Agrilina through Trachyini. Pensoft Series Faunistica 79:1–722.
Grimaldi, D. and M. S. Engel. 2005. Evolution of the Insects.Cambridge University Press, New York, xv + 755 pp.
Copyright © Ted C. MacRae 2013